1. Field of the Invention
The present invention relates to a new liquid fuel; more particularly, it relates to new ethanol-based liquid fuels which can be used as substitutes for petroleum fuels in conventional engines, such as internal combustion, "diesel," and jet engines, without modification to the engines.
2. The Prior Art
With the steadily increasing demand for liquid fuels and the decreasing supply of petroleum crude oil, researchers have been forced to look to alternative fuels in order to fulfill the future demands for liquid fuels. Recent events throughout the world, including the shortage of petroleum crude oil, the sharp increase in the cost of oil and gasoline motor fuels, and the political instability of some crude oil producing countries, have demonstrated the vulnerability of the present sources for liquid fuel. Nevertheless, even if these supply and economic risks were acceptable, it is clear that worldwide product of petroleum products at projected levels can neither keep pace with the increasing demand nor continue indefinitely. It is becoming increasingly evident that the time will soon come when there will have to be a transition to resources which are more plentiful and preferably renewable.
Ethanol has been recognized as a possible liquid fuel alternative which can be available in significant quantities throughout the remainder of this century. See "The Report of the Alcohol Fuels Policy Review" (Dept. of Energy/Pe-0012, June 1979). However, only in light of the recent rapidly rising costs of petroleum products has the cost of an ethanol-based alternative fuel become economically competitive. It will be appreciated that the blended ethanol-based fuel of the present application, when considered with the continuous method of ethanol production disclosed in copending application Ser. No. 088,196 filed on Oct. 23, 1979, will be not only economically competitive in the existing price market of petroleum fuels, but may even be produced at a cost below that of existing petroleum fuels.
It has long been recognized that ethanol may under the proper conditions be useful as a liquid fuel capable of performing equal to, if not better than, conventional petroleum fuels. However, most of the research in this area is old, having been conducted over fifty years ago, before the discovery of the vast Arabian oil fields. There is a considerable amount of literature relative to various mixtures of ethanol and gasoline. In fact, such mixtures (commonly referred to as "gasohol") are sold for use in typical automobile engines in many outlets in the United States and other countries of the world. Also, ethanol in much higher concentrations has been the basic compenent of the fuels used in certain modified high performance engines, such as in race cars. Nevertheless, there has been little, if any, successful research conducted on the use of ethanol-based fuels in unmodified engines, such as conventional automobile engines.
Researchers have looked to ethanol as a component in conventional petroleum fuels because it has a higher thermal efficiency than ordinary petroleum motor fuels. When burned in typical automobile engines, ordinary petroleum fuels convert only about a quarter of the energy of the fuel into useful work, i.e., ordinary motor fuels only have about a 25% thermal efficiency. However, experiments have shown that when about 10% to 25% ethanol is blended with conventional petroleum fuels, the resulting fuel has a slightly greater thermal efficiency than straight petroleum fuel. Other studies have shown that high concentrations (about 95%) of ethanol can be burned in modified engines with much greater thermal efficiency than conventional petroleum fuels. Nevertheless, still other studies using engines designed to run on conventional petroleum fuels have shown that in terms of power, 100% ethanol fell short delivering the power of ordinary petroleum fuels.
Accordingly, those skilled in the art have generally limited their use of ethanol to that of an additive in petroleum fuels. Until the present invention, it had been thought necessary to significantly modify conventional engines (such as to make modifications in the carburetor or the compression ratio) in order to use a fuel which is predominantly ethanol. In addition, there are several other problems which have led those skilled in the art away from using ethanol as the primary component in a substitute liquid fuel in conventional engines. Such problems, which have heretofore not been solved by those skilled in the art, have been taken into account in the blended ethanol-based liquid fuel of the present invention resulting in blended ethanol fuel which can be used as a substitute for ordinary petroleum fuels in unmodified engines.
For example, ethanol has a lower heating value than gasoline--only about 81,900 BTU per gallon as compared to about 136,500 BTU per gallon of gasoline. While the heat value of a volatile liquid fuel bears little relationship to the power output obtainable from that fuel, it can effect other aspects of engine performance. When running on ethanol, engine temperatures are lower than when running on conventional motor fuels. This is essentially because the higher latent heats of the ethanol give a lower induction-stroke temperature and, consequently, a lower average temperature over the whole cycle. The lower flame temperatures of ethanol also lower the average temperature over the whole cycle. In the case of 95% ethanol, it has been shown that the temperature at the end of compression is about 158.degree. F. lower than the temperature of ordinary petroleum fuels. Furthermore, the maximum flame temperature attained by 95% ethanol has been shown to be approximately 225.degree. F. lower than ordinary petroleum fuels. Hence, the transfer of heat to the cooling water is substantially reduced. This reduction in the cooling water temperature may be advantageous under certain operating conditions, such as in hot summer weather or in hilly or dusty terrain. However, this lower cooling water temperature can create substantial problems in starting the engine and can require a much longer period for the engine to become thoroughly warmed up, especially in winter weather.
Additionally, the stoichiometric air to fuel ratio impacts the difficulty with which a cold engine is started. The air to fuel ratio of ordinary fuel is about 14.6 (that is, for perfect combustion, it takes 14.6 volumes of air to one volume of vaporized fuel), whereas the proper stoichiometric air to fuel ratio for ethanol is only about 9.0. Therefore, when ethanol is used as a fuel in a carburetor set for ordinary fuel, the ethanol, which only needs 9.0 volumes of air, is actually receiving 14.6 volumes. The result is that more air is in the mixture than is needed, and the mixture is said to be "lean." This results in a cold engine being much more difficult to start with ethanol than with ordinary fuels. Furthermore, as indicated previously, studies have shown that when a 100% ethanol fuel is used in a typical automobile engine, the fuel fell short in terms of power as compared with straight gasoline or blends of about 10% to 25% ethanol and gasoline. This has been directly attributed to the fact that the 100% ethanol fuel was running on a "lean" mixture. This is one of the reasons that prior art attempts to using an ethanol-based fuel have required significant modifications to the engine, particularly in the carburetion system.
Another significant problem encountered by the prior art in using ethanol as a fuel is that of phase separation. When ethanol and hydrocarbon fuels (such as gasoline) are blended together, the addition of even a small amount of water to the fuel blend will cause the gasoline, ethanol, and water components to separate. This has been one of the significant problems with gasohol where extreme care has been taken to make sure that there is no water in the fuel. The significance of the phase separation problem becomes apparent when it is appreciated that 100% ethanol is difficult to obtain since ethanol can ordinarily only be distilled in a concentration of 95% ethanol, the remaining 5% being water; expensive and time-consuming operations are necessary to remove this last 5% water.